1. Field of the Invention
The present invention relates to an audio and/or video data transmitting apparatus for transmitting digital audio and/or video data via an asynchronous transfer mode (ATM) communication line or the like and a system and method of the same.
2. Description of the Related Art
Compression and coding systems such as the MPEG (Moving Picture Experts Group) 2 system have come into practical use for compressing and coding the audio data and video data (audio and/or video data) of moving pictures such as movies.
Further, as a system for transmitting extremely large volumes of data, for example, audio data, the ATM system has been proposed. Studies are now being made on transmitting the audio and/or video data compressed and coded by the MPEG2 system or the like via an ATM system or other high speed digital communication lines.
When audio and/or video data compressed and coded by the MPEG2 system (compressed audio and/or video data) is transmitted via a communication line of the ATM system, the compressing and coding apparatus on the transmission side must control the amount of data of the generated compressed audio and/or video data (code generation amount control (rate control)) so that neither overflow nor underflow occur in a video STD buffer (VBV (video buffer verifier) buffer) and an audio STD buffer (ABV (audio buffer verifier) on the reception side.
The compressing and coding apparatus on the transmission side has to perform the rate control while calculating the remaining capacity of the STD buffers on the reception side. However, the calculation of the remaining capacity of the STD buffers on the reception side is complex and difficult.
Further, when the timing of the compression and coding on the transmission side is poor, depending on the remaining capacity, there is a possibility that the overflow and underflow (breakdown) will be caused in the STD buffers on the reception side. Further, a multiplexing device performs multiplexing for each elementary stream of the compressed audio data and compressed video data to a predetermined transport stream so as not to cause a breakdown in the STD buffers. When the plan is inadequate, even if the rate control of the elementary stream generated by the compressing and coding apparatus is correct, a breakdown sometimes will occur in the STD buffers.